Breast cancer is a major and often fatal disease for women. There is ample evidence that both mortality and morbidity can be reduced by early detection. The sensitivity of conventional mammography for breast cancer detection is often limited because of inefficiencies of conventional screen-film imaging technology. Phase I research has demonstrated the feasibility and potential of a hybrid silicon pixel detector for application to digital mammography. Development and fabrication of a fully functional prototype scanning digital mammography sensor is proposed for Phase II. The prototype system will be tested using mammography phantoms. It is expected to have high spatial resolution ( approximately 12 lp/mm) wide linear dynamic range (greater than or equal to 4,096 (12 bits)) and high sensitivity. Both MTF and DQE will be significantly improved which could result in earlier detection of breast cancer, particularly in women with dense breasts. Computer based data acquisition allows image processing and enhancement during post examination. X-ray film and film development are eliminated. During Phase III, the Phase II prototype will be improved and a commercial version will be designed and manufactured. The new sensors may be used in clinical trials at collaborating medical institutions. PROPOSED COMMERCIAL APPLICATION: The results of the Phase II and III programs will be a low-dose high resolution digital mammography system with wide linear dynamic range and high signal-to-noise ratio. Modified versions of this technique can be used for medial, industrial and scientific imaging of x-rays from 10 to 100 keV.